1. Field of the Invention
This invention relates to a sewage lifting station. In particular, the invention relates to a sewage lifting station having a closing device whose operation is dependent on the operation of the pump.
2. Description of the Prior Art
Sewage lifting stations have been known, as shown in German Patent 36 07 353. The known sewage lifting stations have two solid waste collection chambers into which the waste water carrying the solid waste is fed. There is also a common collection tank for the waste water that has been freed of solid waste and pre-treated, which flows from each solid waste collection chamber into the main collection tank. Each solid waste chamber is equipped with a pump to drain each collection chamber. The pump pumps and moves a stream of waste water through the individual solid waste collection chamber and into a pressurized pipeline.
With this known sewage lifting station, a closing device is allocated to each connecting pipe and is designed to open or clear an exit orifice in the connecting pipe to the collection tank. The device also at least partially cuts off the connection to the pump in question so that the pre-treated waste water, either in its entirety or the greater part of it, may flow into the collecting tank through the exit orifice and not through the pump. Whenever centrifugal pumps are used, there will be no damage if a small portion of the waste water flows through the pump and rinses it clean.
Furthermore, the closing device is designed to block the exit orifice and close it whenever the pump is in operation draining the collection tank. The closed exit orifice ensures that the entire waste water volume handled by the pump ends up in the pressure pipeline and not pumped back into the collection tank.
In the known sewage lifting station, the closing device is a spring-loaded backflow regulator door which springs into a position where it partially blocks the connecting pipe to the pump. Simultaneously, the exit orifice in the connecting pipe leading directly into the collection tank is unblocked. Whenever the collection tank is filled and the level-controlled pump is switched on, the backflow regulator door is moved against the spring power by the force of the sewage into a position where it closes the exit orifice in the connecting pipe.
The actuation of the known closing device in the shape of a backflow regulator door is thus achieved by the force of the spring and the force of the hydraulic current of waste water.
In actual operation, the known sewage lifting station has performed satisfactorily. However, during operation, the backflow regulator door unit bangs loudly whenever the backflow door closes the exit orifice in the connecting pipeline. Such banging may cause mechanical vibration, which may travel along the pipelines and may be perceived as "loud bangs".
Under extreme operational conditions of the sewage lifting station, e.g. during cloudbursts producing large accumulations of water, undefined switching modes of the backflow door may occur. This may be traced back to the setting of the spring pressure acting onto the backflow shutter at that time. Moreover, the design of the known sewage lifting station may be comparatively expensive because of the large number of necessary individual parts, as well as the necessary adjustment work for the restoring force of the spring.